The invention relates to a frequency adaptive harmonic current generator developed for generating and measuring defined, steady and high-accuracy current harmonics. The invention is a frequency adaptive harmonic current generator, characterized by comprising a microcontroller board (15) used for controlling the generation of harmonic currents and frequency adaptive operating function; an electronic relay (11) controlled and switched over the digital output of the microcontroller (21), the resistor (23) and the transistor (24); a data collection unit (13) to which the voltage divider (5), the buffer (6) and the current shunt (8) are connected for the measurement of voltage and current harmonics and which reads the current and voltage values and transfers such values to the panel type computer (14); and a panel type computer (14) which includes software for making, presenting and recording the measurements, the external connections of which are ensured by USB connectors (18) and a LAN connector (19), which displays the measurement values to the user, and which has push-button (20) for switching on/off operations.